The ceasefire took effect from 6 p.m. on Monday and any member of the Machar-led forces who surrendered must also be protected, Makuei said.
The UK, Germany, India, Japan, Italy and Uganda have been flying out their nationals on military and chartered planes, as commercial flights in and out of the country remain grounded.
The Government of India has chose to send two C-17 military transport aircraft to war torn South Sudan's capital city Juba today to evacuate over 600 Indians stranded there.
The South Sudanese government was committed to the peace agreement signed in August 2015 that ended almost two years of civil war, said James Pitia Morgan, South Sudan's permanent representative to the African Union.
Those who made it across said South Sudanese soldiers were preventing people from crossing, or relieving them of their possessions before allowing them to pass.
The Chinese embassy in South Sudan issued a travel notice this week warning citizens not to travel to the country, and that if they insisted on such a visit they "could face extremely high risks and not be able to receive timely assistance".
South Sudan president Salva Kiir Monday evening ordered a ceasefire after days of heavy fighting between government troops and forces loyal to Vice President Riek Machar in Juba. Government forces have been reported to prevent aid workers from helping civilians.
Supporters of Kiir and Machar fought a civil war beginning in December 2013 that left tens of thousands dead.
Italy's foreign ministry said air force aircraft landed Wednesday in Juba to evacuate 30 Italians who made a decision to leave. Many cars had been shot at or burned.
While South Sudan's government has given a death toll for the weekend's fighting of at least 272, including 33 civilians, Ladsous said he's "convinced, however, that this is only the tip of the iceberg, given alarming reports over the last few days indicating that civilians were barred from safer grounds, including United Nations compounds".
The United Nations is considering an emergency request from East African leaders to send an intervention brigade to Juba that could secure the airport and separate the warring sides.
The Security Council is also considering an appeal from Ban for an arms embargo to be imposed on South Sudan and sanctions targeted at those responsible for the violence.
"There is hardly any food in the market, and people are starving. As a result, they are turning to coping mechanisms like looting to survive", said Jeremiah Young, policy adviser for World Vision. The town is Machar's birthplace.